LEASE, Hilary M.; WOLF, Blair O.; HARRISON, Jon F.; Univ. of New Mexico; Univ. of New Mexico; Arizona State Univ.: Ontogeny of Tracheal Volume in Schistocerca americana

Respiratory systems play a critical intermediary role in the delivery of oxygen from the atmosphere to the cell. Morphological and functional characteristics of respiratory systems thus are often correlated with metabolic functions of animals. We describe a new method to measure the tracheal volume of insect respiratory systems. We use an inert gas displacement technique controlled by a solenoid-flushing device, in conjunction with a gas chromatograph, to measure the tracheal volume of insects in a way that is both reproducible and non-DGC dependent. Animals are first equilibrated with a heliox mix for 3 minutes. Then the animal chamber is flushed with nitrox, and sealed. After 5 minutes, a gas sample is taken from the chamber, and the helium content of the air is measured via a gas chromatograph with a thermoconductivity detector. Chamber helium concentrations are then used to estimate insect tracheal volume. We first describe and show data from a series of experiments that validate this new method. We then use data obtained via this method to investigate the ontogeny of tracheal volume in Schistocerca americana, and to demonstrate this method�s potential application for investigating other physiological patterns.